[Rutherford]

How many co-ordinate bonds are present in the nitrate anion?

By drawing the structure I would say 2, but I don't understand how they have formed. Nitrogen should have 6 electrons so that 2 electrons would make with an O atom a double cov. bond, and the other 2 electron pairs would be donated to the other 2 O atoms. Does this mean that nitrogen that makes NO₃^- should be negative charged, so after the donating of the 2 pairs it gets positive and the 2 oxygen negative (the compound is then negative as it is)?

[fledarmus]

How many co-ordinate bonds are present in the nitrate anion?

 Nitrogen should have 6 electrons ...

Why?

[AWK]

http://en.wikipedia.org/wiki/Nitrate
Each pair + - (in this case one) is an equivalent of co-ordinate bond.

[Rutherford]

So, there are 2.

[AWK]

I cannot find two + singns.

[Rutherford]

But there are 2+- pairs  .

[AWK]

Removing one +- pair only one - remains.

[Rutherford]

I understand now, I could draw the sturcture with the dots and it was ok, maybe it's better to use arrows instead of the + and - because it confuses a lot. Thanks for the help.

[AWK]

arrow is an equivalent to +^__- sign

[Rutherford]

Yes, and it is less confusing, because the +- don't indicate ions, they indicate to which atom is the electron pair closer after donating.

[Rutherford]

Are in B₂H₆ 2 co-ordinate bonds?

[UG]

They are three-center two-electron bonds

[AWK]

http://en.wikipedia.org/wiki/Diborane

[Rutherford]

So, there is an even more complicate bond. Thanks.